It’s been five years since Guillermo del Toro’s last film, and between the problems he faced working on the “Hobbit” movies and trying to get passion project “In the Mountains of Madness” off the ground,” you could hardly blame the guy if he had just called it quits. But instead of getting frustrated by the Hollywood system, he gave them exactly what they wanted: an action-packed blockbuster that also appealed to his inner 12-year-old. “Pacific Rim” is about as close to a Transformers/Godzilla mash-up as you’ll ever see, so it’s not surprising how quickly fanboys jumped on the bandwagon. Unfortunately, the film lacks the uniqueness of the director’s other projects, because while it may not be based on a preexisting property like a lot of summer fare, it still feels oddly generic. That being said, you definitely won’t be bored, and that’s to the credit of the rich mythology that del Toro has created.

Set in the not-too-distant future, giant beasts (referred to as kaiju) have emerged from an inter-dimensional rift below the Pacific Ocean to wreak havoc on every major coastal city from San Francisco to Tokyo. In response, the world’s governments came together to build giant robots called jaegers to combat these monsters, with two pilots controlling each machine via a neurological sync known as drifting. The more compatible the pilots, the better they perform. Though successful for several years, the jaeger program has become increasingly less effective as the kaiju continue to adapt and evolve. When the program is ordered to be shut down, commanding officer Marshall Pentecost (Idris Elba) recruits a retired jaeger pilot named Raleigh (Charlie Hunnam) to team up with rookie Mako Mori (Rinko Kikuchi), with whom he shares a particularly strong connection, and spearhead one final attack in the fight for humanity’s survival.

The marketing campaign for “Pacific Rim” focused almost entirely on the robots vs. monsters angle, but surprisingly, the character-based stuff is a lot more interesting than the action. Elba and Charlie Day (who’s like the spiritual love child of Rick Moranis and Martin Short), are both really entertaining in their respective roles. Elba is one of the few actors with the ability to make such cheesy dialogue sound cool (“Today, we are cancelling the apocalypse!” is this year’s “Release the Kraken!”), while Day, playing one part of a scientific duo trying to find a solution to the kaiju invasion, gets to flex his comedic skills alongside del Toro regular Ron Perlman in a fun cameo. Sadly, Hunnam and Kikuchi are pretty bland as the main protagonists. The former, in particular, still hasn’t found his footing on the big screen despite some consistently solid work on the TV drama “Sons of Anarchy,” although it’s hardly his fault here, as the script isn’t exactly overflowing with a whole lot of character development, or good dialogue, for that matter.

The biggest letdown, though, is the action. While it’s hard to deny the gleeful sensation of watching giant robots pummel giant monsters, it starts to get a little repetitive and would have benefited greatly from more distinct battles and creatures. As it is, every major fight sequence takes place either at night in the pouring rain, or underwater where it’s just as murky, and that makes it really difficult to see things clearly, especially when del Toro relies so heavily on extreme close-ups and quick cuts of the action. After all, if you’re going to promise robots vs. monsters, then I should at least be able to make out what’s going on, because for as awesome as some of the creature designs may be, it would have been nice to see them in greater detail.

The film has some other minor flaws, but this is the only one that really matters, mainly because it’s been positioned as the centerpiece of “Pacific Rim” since its inception. While there’s certainly no shortage of CGI-fueled destruction on display (the third act is practically non-stop action), it’s a little underwhelming considering the potential of such a high-concept idea. As a result, you’re left yearning for more beyond what’s just on the surface, and although del Toro teases at digging deeper into the mythology, it feels like he’s holding some stuff back for a sequel should the first movie perform well. That’s not necessarily a bad thing (you don’t want to blow your wad all at once), but while “Pacific Rim” functions as a fairly enjoyable popcorn flick, it’s lacking any real substance.